This invention relates to a drum brake, such as a parking brake, that is operated by a brake cable; more specifically, it relates to a brake cable connecting apparatus for connecting a brake cable to a brake lever provided in the drum brake.
As a conventional brake cable connecting apparatus for a drum brake, a forward-pull type parking brake apparatus is well-known in the art and consists of a brake lever pivotally supported on a shoe web of a brake shoe at a base portion thereof and a brake cable connected on a free end of the brake lever.
One type of brake cable, for remotely pulling and operating the brake lever, mainly consists of an inner cable, a cable end fixed on a tip end of the inner cable and an outer casing. There is the other type of brake cable without the outer casing, in case of either type of brake cable whether the outer casing is included or not, the term xe2x80x9ccablexe2x80x9d is designated to the part that corresponds to the inner cable in the present specification.
An U-shaped cable-receiving groove is formed at a free end of the brake lever. One end of the cable is connected to a brake operating means such as a hand brake lever in the cabin, and the other or a tip end of the cable penetrates through a back plate and is received in the cable-receiving groove, the cable end securely fixed on the tip end of the cable is engaging with an end edge of the cable receiving groove on the side of a cable releasing direction, thereby preventing the cable from coming off from the cable receiving groove. Actuating the brake operating means such as the hand brake lever for remotely pulling the cable causes the brake lever into rotation and urges the brake shoes to separate apart from each other to effect the parking braking.
Before fixing the brake onto the vehicle, this type of drum brake with the pre-assembled cable causes a drawback by increasing the required stock and transportation space and leaves a potential problem of unexpected damage to the cable during stocking and transportation. Therefore it is preferable that the cable does not connect to the drum brake in the process of drum brake assembly sub-step but in the process of vehicle assembly step.
One idea of a brake cable connecting apparatus, displaying a function of inserting a cable from outside into a drum brake and precisely receiving that cable in a brake cable-receiving groove and further snapping a cable end automatically on an edge surface of the groove at the side of the cable releasing direction, is disclosed in U.S. Pat. No. 5,002,159.
However, the above-described prior art of the brake cable connecting apparatus presents the possibility that the cable end happens to be disengaged from the brake lever if the cable slacks or returns to the initial position earlier than the brake lever when the parking brake is released. As such, an improved brake cable connecting apparatus to overcome such a problem is disclosed as an example shown in FIGS. 16-18 of WO98/40640 Patent Application.
FIG. 16 is a plan view of a leading-trading type (LT type) drum brake (drum brake assembly); FIG. 17 is an enlarged view of a connecting area of a brake cable when seen from arrow A in FIG. 16; and FIG. 18 is a partially enlarged plan view of a connecting area of the brake cable illustrating in FIG. 16.
A pair of brake shoes 1, 2, having an identically structure, are symmetrically disposed on the right and left in FIG. 16 and comprised of the following elements: semicircular shoe webs 1a, 2a; shoe rims 1b, 2b secured to form a T-shape in cross section; and, linings 1c, 2c fixed on a circumferential surface of the shoe rims 1b, 2b, respectively. With shoe holding mechanisms 3, 4, the brake shoes 1, 2 are resiliently mounted on a back plate 11, only a center hole and an opening 11a are shown in the figure with a one dash chain line and a broken line, and lower adjacent ends thereof abut on and engage with an anchor member and are restricted from lifting by a retaining plate 5.
Upper adjacent ends of the brake shoes 1, 2 operationally engage with a pair of left and right pistons of a wheel cylinder 6, respectively. An upper return spring 8 and a lower return spring 9 are stretched between a pair of brake shoes 1, 2 to urge the brake shoes 1, 2 in the retract direction. A brake lever 20 is superposed on the shoe web 1a of one brake shoe 1 and a base portion thereof is pivotally supported on the shoe web 1a with a pin 10. The brake lever 20 is able to rotate with the pin 10 from a position illustrated by a solid line to a position 20xe2x80x2 illustrated by a one-dash chain line in a clockwise direction. A strut 7 provided between the pair of brake shoes 1, 2 restrict return positions of the brake shoes 1, 2 with actions of both return springs 8, 9 by abutting one end thereof on the brake lever 20 provided on one brake shoe 1 and the other end thereof on the other brake shoe 2.
A tongue like piece 20b, formed on the brake lever 20 by partial-shearing, functions as a stopper by abutting on an edged surface closer to the brake center of the shoe web 1a. 
An opening 11a is pierced at the lower left side of the back plate 11 in FIG. 16, and a short conducting pipe 11b is fixed to the opening 11a. A coil spring 31 is compressed from an end of the conducting pipe 11b in the brake to a U-shaped cable end insertion groove 20a formed at a free end of the brake lever 20 by bending. The coil spring 31 urges the brake lever 20 into an initial position illustrated as a solid line and functions as a biasing means to orient the cable end 42 toward the cable end insertion groove 20a upon connecting the brake cable 40 to the brake lever 20.
As shown in FIG. 17, openings 20c is pierced on both side walls of the cable end insertion groove 20a of the brake lever 20 and one end of an L-shaped flap 33 is rotationally attached around a shaft 32 fit into both openings 20c. 
A clockwise rotation of the flap 33 is restricted by abutting a free end thereof against a backward surface (at the side of a cable releasing direction) of the cable end insertion groove 20a as illustrated by a solid line in FIG. 18, while counterclockwise rotation thereof is permitted. A torsion spring 34 wound on the shaft 32 acts on the flap 33 toward the position illustrated as a solid line in FIG. 18; therefore the flap 33 usually covers the cable end insertion groove 20a. Consequently, the flap 33 is only rotated when an external force is added to the flap 33 against the application force of the torsion spring 34. A cable insertion recess 33a is formed at the tip end of the free end of the flap 33.
The brake cable 40 consisted of a cable 41 and a cable end 42 securely fixed to an end of the cable 41. The cable end 42 has a larger diameter than that of the cable 41 and is a bullet-shape at the tip end. The brake cable connecting procedure of the brake cable 40 onto the brake lever 20 will be explained bellow.
The cable end 42 of the brake cable 40, inserted into the opening 11a, passes through the conducting pipe 11=i a =l and reaches the cable end insertion groove 20a while being conducted along by the coil spring 31. Furthermore, the cable end 42 advances inside the cable end insertion groove 20a and pushes the free end of the flap 33, which then is made to rotate and lift the flap 33 in the counterclockwise direction. If the flap 33 rotates to a position 33xe2x80x2 illustrated as a broken line in FIG. 18, the tip end of the flap 33 falls down along a stepped surface 42a of the cable end 42 at a behind end by the resilient force of the torsion spring 34, thereby retracting to the initial position shown the solid line. At the same time, the small stem at the backward half of the cable end 42 is sandwiched between the cable insertion recess 33a of the flap 33 and the bottom of the cable end insertion groove 20a of the brake lever 20 while the stepped surface 42a abuts on and latches with the end surface at the side of the cable releasing direction; therefore, a potential for disengaging the cable end 42 from the cable end insertion groove 20a is restricted if the cable 41 is loosen.
The above-described cable end connecting structure suffers from the following drawbacks and deficiencies.
First, the shaft 32 functioning as a rotation axis of the flap 33 must be installed at a precise position on the brake lever 20 in relation to the cable end insertion groove 20a. Therefore, it is necessary to machine the hole 20c, thereby increasing manufacturing costs.
Secondly, to latch the flap 33 into the stepped portion 42a of the cable end 42, the cable end 42 must advance to the position, illustrated with the broken line, further than that of the normal engaging position illustrated with the solid line in FIG. 18. It is possibility that the cable end 42 might be clamped between the brake lever 20 and an inside surface of the shoe rim 1b, which requires the improved configuration, thereby restricting the design freedom thereof.
Thirdly, to implement the above-described automatic connecting the cable end 42 on the brake lever 20, the conducting pipe 11b and the coil spring 31, conducting the cable end 42 to the end portion of the brake lever 20, must be pre-attached before installing the brake cable 40 to the drum brake, thereby increasing time required to assemble.
The present invention proposes to resolve such problems. It is an object of the present invention to provide a brake cable connecting apparatus without a machining process for ensuring manufacturing (dimensional) accuracy, a necessity of excessive displacement of the cable end 42 further than that of the engaging position, nor an additional effort to assemble the brake.
To attain the above-described object, this invention relates to a drum brake where;
A brake cable connecting apparatus for a drum brake, the apparatus comprising a brake lever for separating the brake shoes apart, the brake lever having a cable end insertion groove for permitting a cable end of a brake cable to pass through, the cable end insertion groove being defined by a lever body and a folded wall at a free end thereof, a guiding means for guiding a the cable end from an entrance of the cable end insertion groove to a position crossing an exit thereof so as to automatically latch the cable end on the brake lever, and a biasing means for flexibly biasing the brake cable inserted from outside of the drum brake toward the free end of the brake lever while deflecting the brake cable. The brake cable connecting apparatus being characterized in that the guiding means is provided between the lever body and the folded wall of the brake lever in a direction toward an opening of the cable end insertion groove adjacent to a tip end of the folded wall or a cross-direction of the brake cable, upon the cable end being fed in a space surrounded by the cable end insertion groove and the guiding means, the guiding means slidably moves in the direction away from a bottom of the cable end insertion groove against an application force of a resilient means so as to permit the cable end from passing through the cable end insertion groove and reach the end surfaces of the guiding means and cable end insertion groove at a cable releasing direction side and characterized in that the guiding means automatically returns by the action of the resilient means to a rest position so as to latch a backward surface of the cable end with the end surfaces of the cable end insertion groove and the guiding means at a side of a cable releasing direction or an exit side of the cable end insertion groove, thereby causing the brake cable to disengage from the brake lever.
This invention is combined with either: an engaging projection formed on the guiding means at the side of the cable releasing direction abutting an end surface of the brake lever at the side of the cable releasing direction; a leading slope for leading the cable end formed on the guiding means at the side of the cable pulling direction; or a leading slope for leading the cable end formed on the cable end insertion groove of the brake lever at the side of the cable pulling direction.
Furthermore, it is combined with: a brake cable including a coil spring wound around the cable thereof and compressed against the cable end; the cable end insertion groove at the side of the cable pulling direction formed to permit the cable end to pass through but obstructing the coil spring from passing through; or the bottom of the cable end insertion groove at the side of the cable releasing direction formed to permit the cable to pass through but obstructing the cable end from passing through; or the biasing means formed as a tail extending from a retaining plate restricting the lifting of the brake shoes; or the biasing means supported by the back plate and a space for guiding the brake cable is formed by the tail and the back plate.